The mother-in-law stopped by her daughter's house after shopping to find her son-in-law boiling angry and hurriedly packing his suitcase.

"What happened?" she asked anxiously.

"What happened? I'll tell you what happened. I sent an email to my wife --- your daughter --- telling her I was coming home a day early from my fishing trip. I got home... and guess what I found? Your daughter in bed with a naked guy! This is unforgivable, the end of our marriage. I'm done. I'm leaving forever!"

"Calm down, calm down!" said his mother-in-law. "There's something very odd about that. She would never do such a thing. There must be a simple explanation. I'll go speak to her and find out what happened."

A few minutes later, the mother-in-law came back with a big smile and said, "I told you there must be a simple explanation --- she didn't get your email."